Method for installing a communication cable assembly

ABSTRACT

Disclosed is a modified pre-ferrulized cable assembly that facilitates installation of an optical fiber communication cable through narrow cable guides having sharp bends. The pre-ferrulized cable assembly includes a communication cable having a free, front end, a semi-finished communication connector, and a suction plug. The invention further relates to efficient methods for installing the modified pre-ferrulized cable assembly through a cable guide.

CROSS-REFERENCE TO PRIORITY APPLICATIONS

This application is a division of commonly assigned U.S. patentapplication Ser. No. 12/685,120 for a Modified Pre-FerrulizedCommunication Cable Assembly and Installation Method (filed Jan. 11,2010, and published May 6, 2010, as U.S. Patent Application PublicationNo. 2010/0111479 A1), which itself is a continuation of commonlyassigned U.S. patent application Ser. No. 12/200,095 for a ModifiedPre-Ferrulized Communication Cable Assembly and Installation Method(filed Aug. 28, 2008, and published Dec. 25, 2008, as U.S. PatentApplication Publication No. 2008/0317410 A1), now U.S. Pat. No.7,665,902.

Parent U.S. patent application Ser. No. 12/200,095 is acontinuation-in-part of U.S. patent application Ser. No. 11/747,573, fora Communication Cable Assembly and Installation Method (filed May 11,2007, and published Nov. 15, 2007, as U.S. Patent ApplicationPublication No. 2007/0263960 A1), now U.S. Pat. No. 7,574,095, whichitself claims the benefit of Dutch Application No. 1,031,792 (filed May11, 2006, at the Dutch Patent Office).

Parent U.S. patent application Ser. No. 12/200,095 further claims thebenefit of U.S. Provisional Patent Application No. 60/969,401, for aModified Pre-Ferrulized Communication Cable Assembly and InstallationMethod (filed Aug. 31, 2007).

Each of the foregoing commonly assigned patents, patent applicationpublications, and patent applications is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

The invention relates to a pre-ferrulized communication cable assemblythat can be readily passed through a cable guide from a startingposition to an end position. The pre-ferrulized cable assembly includesa communication cable having a free, front end, a semi-finishedcommunication connector, and a suction plug. The invention furtherrelates to an efficient method of passing the pre-ferrulized cableassembly through narrow cable guides having sharp bends.

BACKGROUND OF THE INVENTION

When optical fiber networks are installed, the network includes severalconnections for connecting the various end users. Various techniques areused for connecting the optical fiber from the main network to the homesof end users.

One such technique is leading the communication cable through to the enduser's location, after which a so-called communication connector isfitted to the free end in situ. This is not an advisable technique,however, because it is necessary to expose the optical fiber by removingthe cable sheath, to mount the exposed optical fiber end in theconnector, and to polish the end face of the optical fiber so as toenable a good signal transmission.

In another technique, the cable assembly, including a communicationcable provided with a communication connector, is passed through thecable guide to the end position as a pre-prepared assembly. Theconnector, which is likewise passed through the cable guide, hasconsiderable diameter dimensions in comparison with the communicationcable, making it necessary to install comparatively wide cable guides inthe ground. In addition, it is difficult to pass such a cable assembly(i.e., having a complete connector mounted to the free, front end of thecommunication cable) through the cable guide. More specifically, thecable assembly must be passed through the cable guide from the startingposition to its end position. This makes it necessary to carry outoperations at the end position (e.g., in the end user's home), which isundesirable in view of the extent of planning and the man-hoursinvolved.

In yet another, improved technique disclosed in commonly owned U.S.patent application Ser. No. 11/747,573 and its counterpart DutchApplication No. 1,031,792, a semi-finished cable assembly (i.e., apre-fabricated, semi-finished connector secured to a communicationcable) is capable of passing through cable guides having a smalldiameter (i.e., cable guides that are simply too small to permit passageof finished cable assemblies as described previously). This facilitatesthe passage of semi-finished cable assemblies from a central point tovarious end users in a way that the remaining connector can be easilymounted. This improved technique of cable installation significantlyreduces labor costs. Despite the installation efficiencies of the cableassemblies disclosed in U.S. patent application Ser. No. 11/747,573,passage of a partially completed cable assembly remains difficult, ifnot impossible, through sharp bends in narrow cable guides.

Accordingly, it would be desirable to overcome the drawbacks of theknown installation techniques by providing an improved, pre-ferrulizedcable assembly that is capable of ready installation through narrowcable guides, even those having sharp bends.

SUMMARY OF THE INVENTION

Thus, it is an object of the present invention to provide a novel,pre-ferrulized cable assembly (e.g., a partially finished, rigid cableassembly further including a suction plug) that can pass through narrowcable guides having sharp bends, such as cable guides running throughelectrical wall boxes. This may be achieved, for example, by flexiblyaffixing a suction plug to the semi-finished cable assembly disclosed inU.S. patent application Ser. No. 11/747,573 prior to passage through acable guide. (U.S. patent application Ser. No. 11/747,573 is herebyincorporated by reference in its entirety.)

The pre-ferrulized cable assembly is characterized in that, to make itpossible to pass the communication cable through narrow cable guide, theoptical fiber is exposed at the free, front end of the communicationcable. This free end of the cable is fixedly surrounded by a connectingelement, which can be mechanically connected to one or morecomplementary sleeves to complete the communication connector after thecommunication cable has been passed through the cable guide from a startposition to an end position.

Thus, the completed communication connector (i.e., a semi-finishedconnector and a complementary connector) can be connected incommunicative contact to the optical fiber by way of a simple mechanicaloperation after the cable assembly has been led to the end position. Nocomplex and costly finishing operations (e.g., polishing) need to becarried out at the end user's location.

As an example, a suitable semi-finished connector for use according tothe invention is a compact and sturdy Small Form Factor (SFF) ferrule(i.e., the semi-finished connector), which can be blown or pushedthrough narrow cable guides (e.g., cable guides having an outsidediameter of about four millimeters and inside diameter of about threemillimeters). This semi-finished connector can be connected to theremaining connector by a non-expert in the field within a few minutes asan LC compliant (1.25-millimeter ferrule) connector. Those of ordinaryskill in the art will appreciate that such a semi-finished connector isthus practical for FttH installations.

In testing the pre-ferrulized cable assemblies of the present invention,communication cables containing standard G652 D fibers and Single ModePC connectors were used.

The completed communication connectors installed by the method of thepresent invention (i.e., after the installation of the final cableassembly) typically showed insertion loss of less than about 0.5 decibel(and typically about 0.25 decibel) and a minimum return loss of about 45decibels. Those having ordinary skill in the art will appreciate thatsuch results demonstrate an advanced communication connector andinstallation technique.

In accordance with the present invention, the pre-ferrulized cableassembly embraces a spring element that may be positioned around theoptical fiber between the connecting element and the cable sheath(s).The spring element may be retained by the connecting element and aretaining sleeve arranged around the optical fiber. In this way, anyloads exerted on the end faces of an optical fiber and the connectingelement can be absorbed by the compression of the spring element, thuspreventing damage to the connecting element and/or the optical fiber.

The completed communication connector of the present invention has twoprimary components, the semi-finished connector (i.e., the connectingelement and, optionally, the spring element that form a part of thepre-ferrulized cable assembly) and a complementary/snap-on connector(i.e., one or more complementary sleeves that are mechanically connectedto the semi-finished connector after the communication cable has beenpassed through the cable guide).

The connecting element may be provided with at least one recess in itscircumferential surface. This recess may be configured as a circularrecess formed in the circumferential surface in a special embodiment.

According to the invention, to make it easier to pass the pre-ferrulizedcable assembly through the cable guide, the semi-finished connectorportion of the pre-ferrulized cable assembly may be protected by aprotective element that is removably positioned at the free end of thecommunication cable. As herein described, this protective element can beincorporated into a plug assembly that includes a suction plug.

Semi-finished cable assemblies are sometimes unable to pass through abend in a narrow cable guide. For example, when a semi-finished cableassembly passes through a bent section of a cable guide (e.g., amicroduct) with inner diameter D (see FIG. 1), the bend radius of thelatter cannot drop below a certain minimum value R_(b) depending on thelength/and diameter d of the substantially rigid portion of thesemi-finished cable assembly (e.g., the ferrule). The R_(b) value iscalculated using the following equation:

$R_{b} = \frac{\left( {\frac{1}{2}l} \right)^{2} + \left( {D - d} \right)^{2}}{2\left( {D - d} \right)}$

It follows that the ferrule depicted in FIG. 1, which has a length of 22millimeters and a diameter of 2.2 millimeters (including its metalholder), cannot pass bends in a cable guide having an outside diameterof about 4 millimeters and inside diameter of about 3 millimeters (e.g.,having a millimeter diameter ratio of about 4/3) with bend radiussmaller than 75 millimeters. For cable guides having millimeter diameterratios of 5/3.5 and 5/4, the minimum bend radii are 50 and 35millimeters, respectively.

It should be noted that the illustrative ferrule depicted in FIG. 1 hasa constant length and a diameter. In general and for purposes of theR_(b)-value equation, the maximum length and maximum diameter of thesubstantially rigid portion of a semi-finished cable assembly is used.Moreover, for purposes of the R_(b)-value equation the cable itself isdisregarded (i.e., the substantially rigid portion of a semi-finishedcable assembly is deemed not to include the cable itself). It is notbelieved that these simplifying assumptions distort the meaningfulcalculation of the predicted minimum bend radius R_(b).

During testing, it was observed that cable guides having an outsidediameter of about 4 millimeters and inside diameter of about 3millimeters could possess a bend radius as small as 35 millimeters, yetthe ferrule depicted in FIG. 1 could not pass through electrical wallboxes with bend radius smaller than 75 millimeters. This presented aninstallation problem. Previously, to overcome this problem cable guideswere temporarily allowed to hang from wall boxes during the cableinstallation process. This increased the minimum bend radius encounteredby the ferrule depicted in FIG. 1, thereby facilitating cableinstallation (i.e., cable blowing). After installation, the cable guideswere repositioned within the cramped wall boxes.

To facilitate cable installation through a cable guide having a tightbend radius, the pre-ferrulized cable assembly according to the presentinvention includes a suction plug attached to the semi-finishedconnector (and/or a protective element surrounding the semi-finishedconnector). This suction plug facilitates the passage of thepre-ferrulized cable assembly through sharp bends (e.g., the cableguides running through electrical wall boxes) in narrow cable guides.The substantially rigid portion of an exemplary pre-ferrulized cableassembly (i.e., essentially the semi-finished connector and itsprotective cap) has a maximum length of 22 millimeters and a maximumdiameter of 2.2 millimeters. This pre-ferrulized cable assembly(including air suction plug) can pass through cable guides having anoutside diameter of about 4 millimeters and inside diameter of about 3millimeters with bend radius of at least about 35 millimeter. Thus, thecommunication cables attached to semi-finished connectors as in thepresent invention have similar installation capacity as is observed withbare cables (i.e., cables that are not attached to communicationconnectors) with short conical end-cap.

The suction plug of the present invention can be relatively airtight orleaky. For instance, when employing a pulling plug with a leakingaperture, the high-speed airflow partly continues around the pullingplug and partly provides a pulling force. Such a leaking pulling plug isdisclosed in U.S. Pat. No. 5,474,277, which is hereby incorporatedentirely herein by reference. In general, although an airtight suctionplug provides greater pulling force, a leaky suction plug providesbetter performance over longer installation distances.

According to the invention, the communication connector may include atleast one sleeve that is positioned at (e.g., provided around) theconnecting element for use in the final assembly of the cable assembly.

To facilitate the final assembly at the end position, the sleeve may bemade up of two or more sleeve elements to be positioned at (e.g.,provided around) the connecting element.

In a specific embodiment, for example, the sleeve may be provided withfirst and second cams that are spaced apart from one another and thatextend toward the connecting element, with the first cam engaging in therecess formed in the connecting element and the second cam engaging thespring element.

A good mechanical connection of the connecting element to the sleeve orsleeve elements is obtained in this way. In addition, compression of theconnecting element (e.g., as a result of a force being exerted on theend face) can be absorbed by the compression of the spring element.

In another specific embodiment, the second cam mates with a cam presenton the retaining sleeve.

In order to absorb forces being exerted on the end face of theconnecting element through compression of the spring element andmovement of the sleeve, the length of the recess is typically greaterthan the length of the first cam as measured in the longitudinaldirection of the cable.

The communication connector includes a connector housing positioned atthe sleeve (e.g., around the sleeve) to facilitate further assemblyoperations.

According to the invention, to achieve proper retention and to preventthe connector housing from undesirably becoming detached from thesleeve, the connector housing includes a cam extending toward thesleeve. The cam engages in a recess formed in the outer circumference ofthe sleeve.

As noted, the pre-ferrulized cable assembly according to the presentinvention is modified to include a suction plug, which is flexiblyattached to the substantially rigid, semi-finished connector (and/or aprotective element surrounding the semi-finished connector). Thosehaving ordinary skill in the art will appreciate that the substantiallyrigid portion of the pre-ferrulized cable assembly includes thesemi-finished connector its protective cap (i.e., the protectiveelement).

In this regard, this rigid portion of the pre-ferrulized cable assemblytypically has a maximum diameter between about 60 and 95 percent of theinner diameter of the cable guide and, more typically, between about 70and 85 percent of the inner diameter of the cable guide.

Moreover, this rigid portion of the pre-ferrulized cable assemblytypically has a maximum diameter that is less than 200 percent of thediameter of the communication cable, and typically less than 150 percentof the diameter of the communication cable (e.g., 120 percent or less).

The maximum diameter of the communication cable provided with theconnecting element is less than or equal to the diameter of the rigidportion of the pre-ferrulized cable assembly. To facilitate installationof the pre-ferrulized cable assembly, the diameter of the connectingelement can match or be less than the diameter of the communicationcable.

Furthermore, in other embodiments, the length of the rigid portion ofthe pre-ferrulized cable assembly is less than about ten times (10×) itsmaximum diameter, typically less than eight times (8×) its maximumdiameter, and more typically less than six times (6×) its maximumdiameter.

With the foregoing constructional dimensions, a proper and unhampereddisplacement of the pre-ferrulized cable assembly through the cableguide is possible even passing sharp bends in the cable guide.

To facilitate installation of the modified pre-ferrulized cable assemblyaccording to the present invention (i.e., including a plug assembly), adevice for collecting the front end of the pre-ferrulized cable assemblymay be used. Such a device includes an enclosure to be positioned at theend position of the cable guide, the enclosure being provided with oneor more ventilation openings.

This facilitates the collection of the free, front end of thepre-ferrulized cable assembly when it is guided through the cable guidewith the aid of a transfer medium (e.g., gas or liquid). Moreparticularly, the enclosure is configured as a tube-shaped elementhaving a first and second open end, wherein the first open end isprovided with a collar-shaped clamp for coupling with the end positionof the cable guide. This allows a quick and secure coupling anduncoupling of the device to the cable guide at the premises of the enduser (i.e., where the pre-ferrulized cable assembly is to be installedby connecting it with the complementary connector).

In a further embodiment, the second open end is provided with a closurecap, which functions as an end stop for the free, front end of thepre-ferrulized cable assembly upon its emergence from the cable guide.

Moreover, the modified pre-ferrulized cable assembly according to thepresent invention (i.e., including a plug assembly) can be used with atransfer fluid or when water is present in the cable guide (e.g., as aresult of leaking or diffusion). Thus, in a further improved embodiment,the device includes a collecting chamber that accommodates theenclosure, the collecting chamber serving to collect the transfer mediumthat is used in passing the pre-ferrulized cable assembly through thecable guide.

The invention further embraces methods for installing a pre-ferrulizedcable assembly, such as a communication cable having a free end and thatis built up of at least an optical fiber, which is coaxially surroundedby at least one cable sheath. The exemplary method includes the stepsof: (i) providing a cable guide having a starting point and an end pointlocated at an end users home; (ii) guiding the pre-ferrulized cableassembly with the optical fiber being exposed at the free, front end ofthe cable, which end is fixedly surrounded by a connecting element, fromthe starting point toward the end point using a transfer medium; (iii)collecting the free, front end of the pre-ferrulized cable assembly atthe end point; and (iv) mechanically connecting the free, front end ofthe semi-finished cable assembly to one or more complementary sleeves tothereby complete the communication connector. Optionally, step (iii)further includes the step of collecting (at the end point) the transferfluid employed (or water that is simply present) during the guiding(e.g., blowing) of the cable assembly through the cable guide as setforth in step (ii).

In accordance with the foregoing, FIGS. 2A-C illustrate the ease ofattaching the complementary connector to the semi-finished connectorembraced by the present invention. (These photographs, although takenduring testing in which installation of the cable assembly was notfacilitated using a suction plug, are nonetheless illustrative of thefinal assembly of the finished communication connector in accordancewith the present invention.) A semi-finished cable assembly, similar tothat shown, is blown until the end of the cable guide is reached (withair-venting and end-stop). At this point, the suction plug and end cap(i.e., protective element) are removed. Next, the cable boot and a metalcylinder (i.e., sleeves) are sleeved over the ferrule (i.e., thesemi-finished connector). The metal cylinder is then crimped around theferrule and the cable jacket using a crimp tool for extra strength. SeeFIG. 2A. Thereafter, the ferrule is pushed into the connector housing,which is positioned in a holder to simplify this connection. See FIG.2B. Finally, the cable boot is pushed over the metal cylinder therebycompleting the connection of the communication connector.

The pre-ferrulized cable assemblies of the present invention not onlyreduce the time and effort required to install optical cables in an enduser's home, but also reduce the need for subsequent home visits.Blowing of the pre-ferrulized cable assemblies of the present inventionthrough narrow cable guides (e.g., a cable guide having an outsidediameter of about 4 millimeters and inside diameter of about 3millimeters) is possible even for cable guides longer than 1,000 meters.

The foregoing, as well as other objectives and advantages of theinvention, and the manner in which the same are accomplished, arefurther specified within the following detailed description and itsaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a ferrule connected to a cable in asection of bent cable guide.

FIGS. 2A-C illustrate the mechanical connection of a complementaryconnector to a semi-finished connector thereby completing acommunication connector.

FIG. 3A depicts a pre-ferrulized cable assembly (with an airtightsuction plug) according to the present invention.

FIG. 3B depicts a pre-ferrulized cable assembly (with a leaky suctionplug) according to the present invention.

FIG. 3C depicts the substantially rigid portion (A-B) of apre-ferrulized cable assembly according to the present invention.

FIG. 4 shows a prototype pre-ferrulized cable assembly according to thepresent invention.

FIG. 5A depicts a successful installation of a semi-finished cableassembly without the use of a suction plug.

FIG. 5B depicts an unsuccessful installation of a semi-finished cableassembly without the use of a suction plug.

FIG. 5C depicts an installation of a pre-ferrulized cable assembly(including a suction plug) according to the invention

FIG. 6 depicts an embodiment of a semi-finished cable assembly.

FIG. 7 depicts the installation of the semi-finished cable assembly ofFIG. 6.

FIG. 8 depicts a first configuration of a cable assembly in the endposition (i.e., placed for end use).

FIG. 9 depicts a second configuration of a cable assembly in the endposition.

FIG. 10 depicts a third configuration of a cable assembly in the endposition.

FIG. 11 depicts another embodiment of a cable assembly in the endposition.

FIG. 12 depicts yet another embodiment of a semi-finished cableassembly.

FIG. 13 depicts a device for collecting the free, front end of acommunication cable assembly.

FIG. 14 depicts a device for collecting both the free, front end of acommunication cable assembly and installation transfer fluid.

FIG. 15 illustrates a larger-diameter cable guide section installedbetween narrower cable guide sections to facilitate the passage of asemi-finished cable assembly.

DETAILED DESCRIPTION

The present invention is described herein with reference to theaccompanying drawings. As will be appreciated by those having ordinaryskill in the art, these drawings are schematic representations, whichare not necessarily drawn to scale. This invention may be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. The embodiments disclosed are provided toconvey the scope of the invention to those having ordinary skill in therelevant art. In this regard, like parts will be indicated by the samenumerals in the accompanying drawings and following description.

The present invention embraces a partially finished, rigid cableassembly that is modified with a suction plug. The inclusion of asuction plug promotes passage of the pre-ferrulized cable assemblythrough even narrow cable guides having sharp bends, therebyfacilitating installation of an optical fiber communication cable.Exemplary modified pre-ferrulized cable assemblies are schematicallydepicted in FIG. 3A (having an airtight suction plug) and FIG. 3B(having a leaky suction plug). FIG. 3C schematically identifies (i.e.,between line A and line B) the substantially rigid portion of apre-ferrulized cable assembly according to the present invention. Aprototype pre-ferrulized cable assembly according to the presentinvention is shown in FIG. 4.

Accordingly, in one aspect, the modified pre-ferrulized cable assemblyincludes a communication cable 6 that includes at least one cable sheathcoaxially surrounding an optical fiber. The cable sheath typicallyincludes at least one strain-relieving element. A semi-finishedconnector 2, which includes a connecting element 16, is secured to thefree, front end of the communication cable 4. This semi-finishedconnector 2 is in communicative contact with the optical fiber.

The modified pre-ferrulized cable assembly further includes a plugassembly 19, which includes a suction plug 21 (e.g., a suction pig) and,optionally, a protective element 20 (i.e., a cap that protects thesemi-finished connector 2). Stated otherwise, a plug assembly 19embraces the suction plug 21 with or without the protective element 20.The suction plug 21 is secured to the communication cable 6 and/or thesemi-finished connector 2 by a flexible cord 23 or other flexibleattachment section and, optionally, the protective element 20. Wherepresent, the protective element 20 and the suction plug 21 may beremovably connected via the flexible cord 23 or, as depicted in FIGS. 3Aand 3B, fixedly attached via the flexible cord 23. The flexible cord 23may be formed of any suitable material that is both strong and flexible.

The pre-ferrulized cable assembly is passed (e.g., blown) through thecable guide 22 to its destination (e.g., an end user's meter cupboard).Thereafter, the plug assembly 19 is detached of otherwise removed fromthe modified pre-ferrulized cable assembly. The connecting element 16may then be mechanically connected to a complementary connector (notshown here) to form a completed communication connector.

Those having ordinary skill in the art will appreciate that the forcenecessary to remove the plug assembly 19 (i.e., the suction plug 21, theflexible cord 23, and, optionally, the protective element 20) should besufficient to prevent the plug assembly 19 from blowing off when airsuction is applied (i.e., during installation of the pre-ferrulizedcable assembly) but not so great that the removal of the plug assembly19 might break the semi-finished communication connector 2.

Without the use of a suction plug 21, the installation of asemi-finished cable assembly through a cable guide 22 works well atlarger bend radii but becomes impractical, if not impossible, at smallerbend radii. This is schematically depicted in FIGS. 5A and 5B,respectively.

Surprisingly, it has been discovered that the inclusion of a plugassembly 19 promotes local deformation of a cable guide 22 (i.e., amicroduct) during installation of the pre-ferrulized cable assemblythrough tight microduct curves. In particular, the suction plug 21 wasobserved to deform the cable guide 22 at relatively tight bends, therebyfacilitating the movement of the semi-finished communication connector 2and communication cable 6 through the cable guide 22. This unexpectedresult is schematically depicted in FIG. 5C—the deformation of the cableguide 22 is indicated by the two arrows.

As a practical matter, this means that it is now possible to passsemi-finished cable assemblies through cable guides 22 havingsubstantially lower diameters (and/or substantially lower bend radii).Indeed, the pre-ferrulized cable assembly has been found to pass througha bend radius that is significantly less than predicted (e.g., less than75 percent of the predicted minimum bend radius, R_(b) and, in someinstances, less than 50 percent of the predicted minimum bend radius,R_(b)).

Using the pre-ferrulized cable assembly according to the invention, asemi-finished communication connector 2 can be passed through a cableguide 22 together with the communication cable 6 in an effective manner,by using an air suction plug 21 and exerting a pulling or pushing force,which may or may not be provided by a fluid medium (e.g., a gas) underpressure. In this way, no complex assembly operations need to be carriedout at the end position.

As noted and by way of example, the pre-ferrulized cable assemblyaccording to the present invention may be achieved by securing a suctionplug 21 to a semi-finished cable assembly disclosed in U.S. patentapplication Ser. No. 11/747,573. Accordingly, the following discussionof the various semi-finished cable assemblies disclosed therein willenable those having ordinary skill in the art to modify those structuresto achieve pre-ferrulized cable assemblies according to the presentinvention.

In this regard, FIG. 6 depicts one semi-finished cable assembly 1disclosed in pending U.S. patent application Ser. No. 11/747,573. Thiscable assembly 1 is built up of a communication cable 6 that has a free,front end 4. The communication cable 6 can be passed through a cableguide (not shown) to an end position via its free end 4. Thecommunication cable 6 stops when the end position of the cable guide isreached (i.e., due to air-venting end-stop).

The communication cable 6 includes at least an optical fiber 12, whichis coaxially surrounded by at least one cable sheath 6 a as well as astrain-relieving sheath 10. In this embodiment, a buffer sheath 8 isprovided around the optical fiber 12.

To make it easier to pass the communication cable 6 through the cableguide (not shown), the optical fiber 12 is exposed at the free, frontend 4 of the cable 6. The free, front end 4 is fixedly surrounded by aconnecting element 16. The connecting element 16 has a front-end face 16a and a back-end face 16 b, which is in contact with the optical fiber12. The front-end face 16 a is centrally provided with a polished glassfiber surface, which can be placed into communication with a similarpolished surface of a counter connector (not shown). In this regard andby way of example, the front-end face 16 a can be polished under anangle (i.e., an Angle Polished Connector or APC).

The connecting element 16 is provided with at least one recess 18, whichis typically configured as a circular recess formed in thecircumferential surface of the connecting element 16. (The function ofthe recess 18 will be further explained herein.) As depicted in FIG. 6,a spring element 14 is arranged around the optical fiber 12 between theconnecting element 16 and the cable sheaths 8, 10, 6 a. When theconnecting element 16 is fully assembled, the spring element 14functions to press the polished glass fiber surfaces together withsufficient force—but not too much force as mechanical stresses may leadto cracking of the glass material—upon connection with a counterconnector so as to effect a physical contact with a minimal opticalsignal attenuation of the connector connection.

The connecting element 16 and the spring element 14 form part of asemi-finished communication connector 2 (i.e., the semi-finishedcomponent of a communication connector).

The semi-finished cable assembly 1 depicted in FIG. 6 is passed througha cable guide (not shown) in the direction of an end position from acentral distribution point. At the end position, final assembly of thesemi-finished communication connector 2 takes place so that thesemi-finished cable assembly 1 is attached to the complementaryconnector and thus used for communication applications. In other words,the communication connector is completed by attaching the semi-finishedcomponent, which includes the connecting element 16, with acomplementary component, which includes one or more sleeves (e.g., aconnector sleeve 28).

As depicted in FIG. 7, the semi-finished cable assembly 1 is passedthrough an underground cable guide 22 (e.g., a cable conduit). Toprotect the components of the semi-finished communication connector 2(e.g., the connecting element 16 and the spring element 14), aprotective element 20 is used to pass the semi-finished cable assemblythrough the cable guide 22. Protective element 20 protects the free end4 of the semi-finished cable assembly 1 as well as the connectingelement 16 and the spring element 14. See FIG. 7.

The protective element 20 is removable in this embodiment. After thesemi-finished cable assembly has been passed through the cable guide 22to the end position (e.g., an end user's meter cupboard), the protectiveelement 20 must be removed, whereupon the final assembly of thesemi-finished communication connector 2 (at this stage, made up of theconnecting element 16 and the spring element 14) is to take place.

After the semi-finished cable assembly has been passed through the cableguide 22 to the end position (e.g., an end user's meter cupboard), theplug assembly must be removed, whereupon the final assembly of thesemi-finished communication connector 2 (at this stage, made up of theconnecting element 16 and the spring element 14) is to take place.

Upon final assembly and mounting of the communication connector 2, akink protector 24 is slipped over the cable assembly 1. See FIGS. 8-10.Then, a shrink sleeve 26 is fitted around the outer cable sheath 6 a,after which the connecting element 16 and the spring element 14 areprotected by a connector housing (e.g., a connector sleeve 28). In theembodiment shown in FIG. 8, the connector sleeve 28 is built up of twosleeve elements 28 a-28 b, which can be fitted together over theconnecting element 16 and the spring element 14 by way of a clampedconnection or a snap connection.

Each sleeve element 28 a-28 b—depicted in FIG. 8 as sleeve housingelements—is provided with a first inwardly oriented cam 30 a-30 b,which, upon placement around the connecting element 16, extends into therecess 18 of the connecting element 16. See FIGS. 8-10. As shown in FIG.9 and FIG. 10, the length of the recess 18 is greater than the length ofthe first cam 30 a-30 b (as measured in the longitudinal direction ofthe cable 1).

Furthermore, the connector sleeve 28 (i.e., the two sleeve housingelements 28 a-28 b) is provided with a second inwardly oriented cam 32a-32 b that is spaced from the first inwardly oriented cam 30 a-30 b.The second inwardly oriented cam 32 a-32 b engages the spring element14. The spring element 14 is thus retained between the second cam 32a-32 b and the back-end face 16 b of the connecting element 16. Thismanner of retaining the spring element 14 (in conjunction with thelarger dimension of the recess 18 in comparison with the first cam 30a-30 b that extends into the recess 18) enables a slight degree ofcompression of the connecting element 16 as a result of the action ofthe spring element 14 when longitudinal forces are exerted thereon. Inthis way, the optical fiber 12 is not subjected to loads that mayadversely affect it.

As depicted in FIG. 9, the strain-relieving sheath/element 10, which,for instance, may be made of aramid fibers formed around the surfaces 34a-34 b, is provided with a screw, a knurled edge, or otherfriction-increasing surface. The strain-relieving sheath 10 is thusclamped onto the surfaces 34 a-34 b of the two sleeve housing elements28 a-28 b by the shrink sleeve 26. In this way, a good strain-relievingconnection between the communication connector 2 and the outer sheath 6a is realized. The kink protector 24 can be slid in the direction of thecommunication connector 2, so that it protects the shrink sleeve 26 andabuts a first upwardly oriented cam 42 provided on each sleeve housingelement 28 a-28 b.

As depicted in FIG. 10, the free end of the connecting element 16projecting from the connector sleeve 28 is further protected by way of aprotective sleeve 36, which is provided with an inwardly oriented cam 36a. The inwardly oriented cam 36 a precisely fits in the circular recess28′ formed in the external surface of the connector sleeve 28. Theprotective sleeve 36 thus abuts outwardly oriented cam 41, which formspart of each sleeve housing element 28 a-28 b. The final assembly of thecommunication connector 2 is completed by the provision of a connectorenvelope 37, which can be slid over the protective sleeve 36, theupright cams 41-42, and the kink protector 24.

FIG. 11 depicts a cable assembly that includes a one-piece sleevehousing element 28 (but is otherwise similar to that depicted in FIG.10). After positioning the one-piece sleeve housing element 28, thespring element 14 is loaded by pushing ring 38 (previously placed in thesemi-finished assembly) into the sleeve housing element 28. Ring 38snaps into place using recession 40.

In contrast to the embodiments shown in FIGS. 6-11, FIG. 12 disclosesyet another embodiment of a semi-finished cable assembly 1 in which thespring element 14 is not arranged around the optical fiber (not shown).Rather, spring element 14 is provided around element portion 43 abetween the connecting element 16 and the cable sheath 6 a. As isdepicted in the cross-sectional view of FIG. 12, the intermediateelement 43 has a hexagonal outer circumference, around which the sleeveelements 28 a-28 b (not shown) can be clamped. Because of this surfaceconfiguration, sliding or rotating movement is not possible and there isno need for a cam-recess configuration.

In the embodiment depicted in FIG. 12, the connecting element 16 isprotected by a protective element 20, while the spring element 14 andthe ring 38 are protected by a protective retaining sleeve 20 a. Thering 38 is disposed between the spring element 14 and the sheaths 6 a,8, 10 and is provided with internal screw thread for being fitted aroundthe sheath 6 a. The ring 38 functions to hold the protective retainingsleeve 20 a in place. This construction results in a semi-finished cableassembly having a reduced external diameter, which makes it easier topass the assembly through a cable guide 22.

In another embodiment, the protective retaining sleeve 20 a and theprotective element 20 may be configured as one unit, which may have aslightly larger external diameter. A ring 38 may be provided between thespring element 14 (i.e., its upright, circular edge) and the sheaths 6a, 8, 10. See FIG. 11. After the semi-finished cable assembly 1 has beenmoved to the end position and the kink protector 24 and the shrinksleeve 26 have been provided, the ring 38 is pressed down in theconnector sleeve 28. As a result, the spring element 14 is biased. Thering 38 fits in a recess 28 d formed in the inner circumference definedby the sleeve housing elements 28 a-28 b.

FIGS. 13 and 14 disclose a device 46 for collecting the front end of thepre-ferrulized cable assembly according to the present invention. Thepre-ferrulized cable assembly is passed through a cable guide 54, whichends (e.g., terminates), for example, at the home of an end user. Thepre-ferrulized cable assembly is passed through the cable guide 54 usinga transfer medium (e.g., pressurized air or liquid) from a startingposition to an end position 54 a, which is typically located inside theend user's home.

In this regard, the device 46 includes an enclosure 48, which is to beprovided at (e.g., positioned around) the end position 54 a of the cableguide 54. The enclosure 48 is provided with one or more ventilationopenings 50 that allow the passage of the transfer medium (e.g.,pressurized air or liquid) out of the enclosure when passing thepre-ferrulized cable assembly through the cable guide 54.

The enclosure 48 is typically configured to be tube-shaped, having afirst open end 48 a and a second open end 48 b, wherein the first openend 48 a is provided with a collar 56 for coupling with the end position54 a of the cable guide 54. As depicted in FIGS. 13 and 14, the collar56 is a collar-shaped clamp secured to the cable guide 54. The secondopen end 48 b is provided with a closure cap 52.

As depicted in FIG. 14, the foregoing device 46 may further include acollecting chamber 58, in which the enclosure 48 is accommodated. Thecollecting chamber 58 serves to collect the liquid transfer fluid 60that is used for passing the pre-ferrulized cable assembly through thecable guide 54.

The semi-finished cable assemblies disclosed herein are sized tofacilitate a proper and unhampered displacement of a semi-finished cableassembly through the cable guide 54, even passing sharp bends in thecable guide 54.

The exemplary embodiments of the semi-finished cable assembly shown inFIGS. 6-10 may be provided with a connecting element 16 having adiameter of about 1.25 millimeters. The cable 6 has a diameter of about1.8 millimeters, whereas the protective element 20 is about 13millimeters long and has a maximum diameter of about 2.2 millimeters.

Yet another exemplary embodiment embraces a cable 6 having a diameter ofabout 1.8 millimeters with connecting element and a protective element20 having a length of about 20.5 millimeters and a maximum diameter ofabout 2.85 millimeters. This semi-finished cable assembly can be blownthrough a cable guide 22 having a diameter ratio of about 5/3.5 (e.g.,having an outside diameter of about 5 millimeters and inside diameter ofabout 3.5 millimeters).

The exemplary embodiment depicted in FIG. 12 has a reduced diameter asit uses two protective elements (i.e., element 20 placed over theconnecting element 16 and protective retaining sleeve 20 a placed overthe rear assembly). The protective sleeve 20 a can be made of softmaterial (e.g., a heat shrinkable plastic tube) that can later be easilycut away or otherwise removed. The cable 6 has a diameter of 1.8millimeters and protective element 20 has a length of 20.5 millimetersand a maximum diameter of 2.65 millimeters. The semi-finished cableassembly can be blown through a cable guide 22 having an outsidediameter of about 4 millimeters and inside diameter of about 3millimeters.

This configuration, without the protective sleeve 20 a, has been testedby blowing in a 1030-meter trajectory with 180° bends with radius of 15cm placed every 100 meters. With a blowing pressure of 10 bar, the speedat the end was still 14 meters per minute, reducing to 13 meters perminute when the connecting element 16 emerged from (i.e., exited) thecable guide 22. This indicates that no negative blowing effects—therewas, in fact, a small positive effect—were found when installing with asemi-finished connector.

Yet another exemplary embodiment embraces a cable 6 having a diameter ofabout 1.8 millimeters with a protective element 20 having a length ofabout 18.5 millimeters and a maximum diameter of about 3.25 millimeters.This semi-finished cable assembly can be blown through a cable guide 22having a diameter ratio of about 5/3.5 (e.g., having an outside diameterof about 5 millimeters and inside diameter of about 3.5 millimeters). Itis preferable, however, to use a cable guide having a larger diameter(e.g., an outside diameter of about 7 millimeters and inside diameter ofabout 5.5 millimeters).

* * *

Tests with other prototypes were carried out to determine theinstallation viability of a semi-finished cable assembly. For example,tests with prototypes of the semi-finished (1.25-mm) cable assemblieswere performed. It was observed that blowing was possible at 10 bar in acable guide having an outside diameter of about 4 millimeters and insidediameter of about 3 millimeters (e.g., having a millimeter diameterratio of about 4/3) in a standard IEC 60794-5-10, 1000-meter trajectoryincluding 180° bends with bend radius of 160 millimeters every 100meters and a Y-branching duct-connector close to the termination box.There was no loss in performance when compared to blowing acommunication cable without a semi-finished connector attached to it. Atthe end of trajectory, a section of cable guide of a defined length(terminated with air-venting and end-stop) was placed and the cable cameto a full stop automatically when the cable reached the end-stop. Thedefined length was chosen such that the finished connectorized cablematches the length needed in the termination box. The final assembly ofthe communication cable was accomplished without any problems.

The following examples describe testing of the various semi-finishedcable assemblies:

EXAMPLES

For testing various cables assemblies, a microduct (i.e., cable guide)having a length of 100 meters and an outside diameter of about 4millimeters and an inside diameter of about 3 millimeters (e.g., havinga millimeter diameter ratio of about 4/3) was laid on the ground in10-meter loops. Each loop included a 180° bend with a bend radius ofabout 20 centimeters. At around 50 meters (i.e., about midway throughthe microduct), a sharper bend was made with the microduct in a benchvice, in which the bend radius (twice the plate-distance inside thebench vice) could be varied. (In this regard, the bend radius intwo-point bending is a little less than half the plate distance.) Eachcable assembly was blown using a MicroJET EM-25 with an air pressure of10 bar and the magnetic clutch at position 4 (i.e., with a 15 N pushingforce).

First, a bare cable with a short conical end-cap was tested through theaforementioned microduct. The cable passed a minimum bend radius of 35millimeters without speed reduction, reaching the end of the microductwith the speed unchanged at 46 m/min.

Second, a semi-finished cable assembly (i.e., cable and semi-finishedconnector but without suction plug) was tested through theaforementioned microduct. The rigid, semi-finished connector had alength of 22 millimeters and a diameter of 2.2 millimeters. Thesemi-finished cable assembly could pass a minimum bend radius of about75 millimeters, with the same unchanged speed. This result is inaccordance with the equation used to calculate the R_(b) value notedpreviously.

Third, a semi-finished cable assembly (i.e., cable and semi-finishedconnector but without suction plug) was tested through a bent microducthaving an outside diameter of about 5 millimeters and inside diameter ofabout 3.5 millimeters (e.g., having a millimeter diameter ratio of about5/3.5). The rigid, semi-finished connector had a length of 22millimeters and a diameter of 2.2 millimeters. As depicted in FIG. 15,this 5/3.5 section was positioned between cable guide sections having anoutside diameter of about 4 millimeters and inside diameter of about 3millimeters (e.g., having a millimeter diameter ratio of about 4/3).Although the placement of a larger-diameter cable guide sectionfacilitates the passage of the semi-finished cable assembly throughsharp bends, here the minimum bend radius achieved was 55 millimeters.This is slightly larger than predicted in theory (i.e., the R_(b) valueequation), perhaps due to the relatively high stiffness of the microducthaving a millimeter diameter ratio of about 5/3.5.

Fourth, a prototype pre-ferrulized cable assembly according to thepresent invention (i.e., a cable, semi-finished connector, and a suctionplug) was tested through the aforementioned microduct. See FIG. 4.Because no commercial suction plug of the right size was available forthe test, an improvised foam-plug was attached using aramide yarn to anend cap that was positioned on the ferrule (i.e., the semi-finishedconnector). The substantially rigid portion of the pre-ferrulized cableassembly (i.e., essentially the semi-finished connector and itsprotective cap) had a length of 22 millimeters and a diameter of 2.2millimeters. See FIG. 3C. The foam plug, which was capable of pulling asmuch as 7 N when 10 bar air pressure was used, forced the pre-ferrulizedcable assembly through the bent microduct, while temporarily deformingthe microduct locally. The ability of the foam plug to cause meaningfuldeformation of the microduct was unexpected. See FIG. 5. The smallestbend radius reached without speed reduction was 40 millimeters. At abend radius of 35 millimeters, the ferrule became stuck but, after a fewseconds, the pressure behind the foam plug increased. Thereafter, theferrule once again started to move and reached the end of the microductat full speed. It is believed that the pre-ferrulized cable assemblyaccording to the present invention is capable of withstanding a pushingforce of at least about 50 N.

The aforementioned test results demonstrate that a pre-ferrulized cableassembly of the present invention can pass through microducts having amillimeter diameter ratio of about 4/3 and 35-millimeter bend radius.This matches the installation performance (i.e., blowing performance) ofa bare cable with short conical end-cap and significantly exceeds theinstallation performance of other semi-finished cable assemblies. Inthis way, the pre-ferrulized cable assembly of the present inventionprovides the blowing efficiency of a bare cable while retaining thefinal assembly advantages of semi-finished cable assemblies.

In the specification and the figures, typical embodiments of theinvention have been disclosed. The present invention is not limited tosuch exemplary embodiments. Specific terms have been used only in ageneric and descriptive sense, and not for purposes of limitation. Thescope of the invention is set forth in the following claims.

The invention claimed is:
 1. A method for installing a communicationcable assembly, the cable assembly comprising a communication cablehaving a free, front end, wherein the cable includes at least an opticalfiber that is coaxially surrounded by at least one cable sheath, themethod comprising the steps of: providing a cable guide having astarting point and an end point; securing a plug assembly to the cableassembly; guiding the cable assembly, using a transfer medium, with theoptical fiber being exposed at the free, front end of the cable, thefree, front end being fixedly surrounded by a connecting element fromthe starting point toward the end point, wherein the step of guiding thecable assembly through the cable guide comprises the plug assemblyleading the cable assembly through a section of the cable guide that has(i) an inner diameter of 3 millimeters or less and (ii) a bend radius ofless than 75 millimeters; collecting the free, front end of the cable atthe end point; mechanically connecting the free, front end of the cableto a communication connector.
 2. The method according to claim 1,wherein the plug assembly comprises a suction plug for guiding the cableassembly through the cable guide.
 3. The method according to claim 2,wherein the plug assembly comprises a protective element for protectingthe free, front end of the cable.
 4. The method according to claim 1,wherein the step of guiding the cable assembly through the cable guidecomprises the plug assembly leading the cable assembly through a sectionof the cable guide that has (i) a substantially constant inner diameterof 3 millimeters or less and (ii) a bend radius of less than 75millimeters.
 5. The method according to claim 4, wherein the plugassembly leads the cable assembly through a section of the cable guidehaving an outside diameter of about 4 millimeters or more.
 6. The methodaccording to claim 1, wherein the step of guiding the cable assemblythrough the cable guide comprises the plug assembly leading the cableassembly through a section of the cable guide that has (i) an insidediameter of about 3 millimeters or less and (ii) a bend radius ofbetween about 35 millimeters and 55 millimeters.
 7. The method accordingto claim 1, wherein the step of guiding the cable assembly through thecable guide comprises the plug assembly leading the cable assemblythrough a section of the cable guide that has (i) an inside diameter ofabout 3 millimeters or less and (ii) a bend radius of less than about 35millimeters.
 8. The method according to claim 1, wherein the step ofguiding the cable assembly through the cable guide comprises the plugassembly leading the cable assembly through a section of the cable guidethat has (i) a substantially constant inner diameter of about 3millimeters or less and a substantially constant outer diameter of about4 millimeters or more and (ii) a bend radius of between about 35millimeters and 65 millimeters.
 9. The method according to claim 1,wherein, during the step of guiding the cable assembly from the startingpoint toward the end point, the plug assembly causes localizeddeformations in the cable guide to facilitate movement of the cableassembly through the cable guide.
 10. The method according to claim 1,wherein: the cable assembly defines a substantially rigid portion; andthe step of guiding the cable assembly from the starting point towardthe end point comprises guiding the cable assembly through a cable guidebend that defines a bend radius that is less than the predicted minimumbend radius R_(b) according to the following equation:$R_{b} = \frac{\left( {\frac{1}{2}l} \right)^{2} + \left( {D - d} \right)^{2}}{2\left( {D - d} \right)}$wherein, D is the inner diameter of the cable guide; l is the maximumlength of the substantially rigid portion of the cable assembly; and dis the maximum diameter of the substantially rigid portion of the cableassembly.
 11. The method according to claim 1, wherein: the cableassembly defines a substantially rigid portion; and the step of guidingthe cable assembly from the starting point toward the end pointcomprises guiding the cable assembly through a cable guide bend thatdefines a bend radius that is less than about 75 percent of thepredicted minimum bend radius R_(b) according to the following equation:$R_{b} = \frac{\left( {\frac{1}{2}l} \right)^{2} + \left( {D - d} \right)^{2}}{2\left( {D - d} \right)}$wherein, D is the inner diameter of the cable guide; l is the maximumlength of the substantially rigid portion of the cable assembly; and dis the maximum diameter of the substantially rigid portion of the cableassembly.
 12. The method according to claim 1, wherein: the cableassembly defines a substantially rigid portion; and the step of guidingthe cable assembly from the starting point toward the end pointcomprises guiding the cable assembly through a cable guide bend thatdefines a bend radius that is less than about 50 percent of thepredicted minimum bend radius R_(b) according to the following equation:$R_{b} = \frac{\left( {\frac{1}{2}l} \right)^{2} + \left( {D - d} \right)^{2}}{2\left( {D - d} \right)}$wherein, D is the inner diameter of the cable guide; l is the maximumlength of the substantially rigid portion of the cable assembly; and dis the maximum diameter of the substantially rigid portion of the cableassembly.
 13. A method for installing a communication cable assembly,the cable assembly comprising a communication cable having a free, frontend, wherein the cable includes at least an optical fiber that iscoaxially surrounded by at least one cable sheath, the method comprisingthe steps of: providing a cable guide having a starting point and an endpoint; securing a plug assembly to the cable assembly; guiding the cableassembly, using a transfer medium, with the optical fiber being exposedat the free, front end of the cable, the free, front end being fixedlysurrounded by a connecting element from the starting point toward theend point, wherein the step of guiding the cable assembly through thecable guide comprises the plug assembly leading the cable assemblythrough a section of the cable guide that has (i) an inner diameter of 4millimeters or less and (ii) a bend radius of less than 50 millimeters;collecting the free, front end of the cable at the end point;mechanically connecting the free, front end of the cable to acommunication connector.
 14. The method according to claim 13, whereinthe step of guiding the cable assembly through the cable guide comprisesthe plug assembly leading the cable assembly through a section of thecable guide that has (i) a substantially constant inner diameter ofabout 3.5 millimeters or less and (ii) a bend radius of less than 50millimeters.
 15. The method according to claim 14, wherein the plugassembly leads the cable assembly through a section of the cable guidehaving an outside diameter of about 5 millimeters or more.
 16. Themethod according to claim 13, wherein the step of guiding the cableassembly through the cable guide comprises the plug assembly leading thecable assembly through a section of the cable guide that has (i) asubstantially constant inner diameter of about 4 millimeters or less and(ii) a bend radius of less than 35 millimeters.
 17. The method accordingto claim 16, wherein the plug assembly leads the cable assembly througha section of the cable guide having an outside diameter of about 5millimeters or more.